ESPE Abstracts

Background: Progressive Osseous Heteroplasia (POH) is characterised by heterotopic ossifications in a deep muscle and fascia. To date, GNAS1 gene loss-of-function mutations on paternal allele were reported as responsible for POH. Unlike other GNAS1 related diseases such as pseudohypoparathyroidism 1a (PHP1a) or pseudopseudohypoparathyroidism (PPHP), patients with typical POH do not show hormonal resistance (HR) or Albright hereditary osteodystrophy (AHO). But some patients diagnosed as POH with HR and/or AHO were reported previously as overlapping syndrome with POH/PHP1a or POH/PPHP.

Objective and hypotheses: The aim of this study is to investigate the degree of HR in four patients with clinically diagnosed as POH in our hospital.

Method: We checked medical records retrospectively and evaluated HR with focuses on TSH and PTH. We also performed gene analyses of the patients and/or their parents.

Results: Patient 1 showed no abnormality with TSH or PTH. Patient 2 showed transient increase in PTH without abnormalities in Ca, P and thyroid function from the age of 3–5 years. Patient 3 showed persistent elevation of PTH without abnormalities in Ca, P and thyroid function from the age of 8 years. Patient 4 showed TSH elevation from neonatal mass screening and PTH elevation with hypocalcaemia from the age of 5 years. All of four patients have heterotopic ossifications in a deep muscle of the shoulder, elbow, calf or heel. Patients other than patient 1 showed some symptoms with AHO. All of them have mutation of GNAS1 gene and the mutation was proved on the paternal allele in patient 1.

Conclusion: POH patients could be accompanied with variable degree of HR. Further study other than GNAS1 gene mutation analyses might be necessary to understand the mechanisms for these variable HR with POH patients.